The Steam overlay on PS3 will let players access Valve's online service from the console.

After months of letting fans wonder how Steam might work on the PS3, today Valve announced how the two systems will sync up. According to the suburban Seattle developer, Steam will offer Portal 2 players "cross-platform matchmaking, gameplay, friends, chat, and achievements."

Using the Steam Cloud feature, it will also offer online saves of both co-op and single-player games that can be accessed from any online PS3. PS3 Portal 2 purchasers can also get a free PC or Mac edition of the game via a one-time Steam download code included with the game. [CORRECTION: GameSpot initially reported you could access PS3 Portal 2 game saves on other platforms, which is not the case.]

Steam for the PS3 will also let players look up both their PlayStation Network and Steam friends and offer rapid access to game invites, friend requests, player profiles, and text chat. In addition, Steam achievements in Portal will be "earned in lockstep" with PlayStation Trophies, once players link their PSN ID and Steam accounts.

Instructions on how to use Steam on the PS3 can be found on the Steam Support Knowledge Base. Portal 2 will debut on the platform--and the PC and Xbox 360--on April 19.